The present invention relates generally to a semiconductor device, and in particular to a semiconductor device capable of enhanced operating margin and reduced power consumption.
Performance characteristics of MOS transistors based upon device current may be categorized into a typical condition, a slow condition and a fast condition. The typical condition represents transistors which are included in a typical group that falls within a performance characteristic range, based upon device current, which is generally desired by manufacturers in order to satisfy semiconductor device performance requirements. The slow condition represents transistors which are included in a group that has inferior current characteristics (that is, a group that has a lower device current) when compared to the transistors belonging to the typical group. The fast condition represents transistors which are included in a group that has superior current characteristics (that is, a group that has greater device current) when compared to the transistors belonging to the typical group. Such differences operating current characteristics (or performance characteristics) of transistors may be due to process variations, for example. It is known that current characteristics of transistors may be changed by variations in the thickness, width/length, sheet resistance and threshold voltage of each of the gate dielectric layers. For reference, in the present specification, a skew may indicate a change in the characteristic of a transistor due to the influence of process variations or the like.